Extremely low-wind conditions in the first quarter of this year across much of the United States have caused low generation at numerous wind farms and a great deal of concern about future performance.
Vaisala’s analysis and Q1 U.S. Wind Performance maps capture and confirm these observations. The company’s climate scientists have been tracking and analyzing the event through their continually updated historical database and have flagged several extreme anomalies, particularly in the West.
In January, nearly all states west of the Rocky Mountains experienced wind speeds at least 20% below their long-term monthly average, which is usually the lowest extent shown in Vaisala’s studies. However, within that same month some areas saw wind speeds nearly 50% below average, effectively “breaking” the typical scale. Widespread low-performance continued to a lesser extreme in February, but returned strongly in March with a vast majority of the country seeing wind speed anomalies 20% or more below normal. Popular wind regions like Texas, California, and parts of the Midwest were particularly hard hit given their large concentration of operating wind assets.
An anomaly of this magnitude, covering such a large area, has caused a great deal of alarm amongst operators, some of whom generated less than half of the energy they produced last year during the same time period. Many are asking themselves, “How could something like this happen?”
Vaisala’s investigation has identified a low-wind pattern across the U.S. with a large blocking high-pressure system over much of the West. The polar jet stream was also much further north compared to last year. This resulted in above-normal wind speeds in central Canada and some border states, and a mild winter in much of the West. Weak surface pressure gradients and light southerly winds in March were particularly challenging to many projects across Texas.
Without a doubt a low-wind event can be worrying, and Vaisala is working closely with clients to evaluate what it means for the future. While a tentative outlook for Q2 2015 indicates a return to more typical conditions, incidents like this underscore the importance of having a long-term perspective on wind variability for operating and pre-construction projects.
Operators must understand the cause of a project’s over or under-performance and reconcile it against long-term conditions at a location. For investors it is particularly critical to understand long-term climate and weather patterns at a proposed site (in terms of extreme highs and extreme lows) when drawing conclusions about future performance based on past observations.
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